The foraging ecology of an oceanic squid, Todarodes filippovae: The use of signature lipid profiling to monitor ecosystem change

Signature lipid/fatty acid and stomach content analyses were used in combination to examine the feeding ecology of Todarodes filippovae, an abundant oceanic squid with a broad circumpolar distribution in continental slope waters in the Southern Ocean. Both techniques show a diet that is closely linked to prey availability and abundance, with some specialisation occurring for Myctophid fishes which dominated the diet numerically and taxonomically. Mean monthly differences in total lipid content of the digestive gland correlated with satellite-derived sea surface chlorophyll, illustrating that the diet is closely linked to short-term (monthly) temporal changes of primary productivity. Multidimensional scaling analysis of prey and T. filippovae signature fatty acid profiles revealed apparent intra-specific predator to prey relationships. Significant season versus site interactions for various lipid classes and fatty acids were observed, further indicating that temporal dietary shifts are related to site-specific oceanography and ecosystem structure (prey composition and/or productivity). Comparing fatty acid profiles with other Southern Ocean squid species, interspecific similarities and differences in diet composition were evident. Results demonstrate that signature lipid profiling of squid can be used as a complimentary or even alternative and cost effective tool to examine key changes in prey-community structure and ecosystem productivity. Such knowledge is fundamental to better understanding the effects of environmental perturbations from fisheries, climate change and pollution.